Clin Physiol Funct Imaging (2015) 35, pp120–126
doi: 10.1111/cpf.12135
Shuttle walking test in obese women: test-retest reliability and concurrent validity with peak oxygen uptake €rgensen1, Renata Trimer1, Victor Z. Dourado2, Luciana Di Thommazo-Luporini1, Soraia P. Ju audio R. Oliveira4, Ross Arena5, Renata G. Mendes1 and Audrey Borghi-Silva1 Jose C. Bonjorno-Junior3, Cl 1
Cardiopulmonary Physiotherapy Laboratory, Federal University of Sao Carlos, Sao Carlos, 2Department of Human Movement Sciences, Laboratory of Human Motricity, Federal University of S~ao Paulo, Santos, 3Department of Bioengineering, University of Sao Paulo, 4Department of Medicine, Federal University of Sao Carlos, Sao Carlos, Brazil and 5Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois Chicago, Chicago, IL, USA
Summary Correspondence Audrey Borghi-Silva, Federal University of Sao Carlos (UFSCar), Cardiopulmonary Physiotherapy Laboratory – Physical Therapy Department, Rodovia Washington Luis, Km 235-SP310, Sao Carlos, 13565-905, Sao Paulo, Brazil E-mail: [email protected]
Accepted for publication Received 23 October 2013; accepted 13 January 2014
Key words cardiopulmonary response; metabolic stress; obesity; oxygen uptake; physical capacity; submaximal exercise testing; women
Objective The aim of this study was to evaluate the test–retest reliability, concurrent validity and agreement with peak oxygen uptake (VO2) obtained during cardiopulmonary exercise testing (CPX) on a treadmill for the incremental shuttle walking test (ISWT) in obese women. Methods Prospective study with a convenient sample of 46 community-dwelling obese women (BMI > 30 kg m2). The main outcome measures were walking distance on the ISWT and peak VO2. Results Test–retest reliability was good to excellent for the exercise tests (ISWT distance ICC: 090; and CPX peak VO2 ICC: 090). Peak VO2 obtained during CPX correlated significantly with ISWT distance (r = 054, P08 good;
>09 excellent; Cronbach, 1951); (iv) Pearson’s or Spearman’s coefficient of correlation to study the correlation between variables [perfect correlation (r = 1), strong (r > 075), moderate (r > 05), weak (r < 05) and non-existent (r = 0)]. The level of statistical significance was set at P40 kg m2). Regarding self-reported physical activity, 83% of the participants evaluated in this study were considered sedentary and 17% reported a normal physical activity index. None of the subjects included in this analysis had a high level of physical activity (Pepera et al., 2013). Of hypertensive volunteers (n = 8), all were managed pharmacologically and showed no hypertensive crisis. As demonstrated in Table 2, there was no statistical difference for any variable analysed between ISWT2 and ISWT3. During ISWT2, the group walked an average of 82 16% of the predicted distance, and during ISWT3, this value was 83 17% (P = 084). Several key variables were selected to assess the reliability between ISWT2 and ISWT3: HR, respiratory rate (RR), VO2 and ISWTD. We observed that the mean difference between these variables approximated zero, suggesting good concordance between ISWT2 and ISWT3 (Fig. 1). The reliability of key variables is listed in Table 3; all demonstrated high reliability, in particular, ISWTD. As there was no significant difference between the values obtained for ISWT2 and ISWT3, the former was selected for a validation analysis in comparison with the data obtained from the CPX on a treadmill. It was noted that the ISWT represented near-maximum effort in this population with a mean HRmax value of 83 9%, while the CPX was consistent with maximal effort and had a HRmax average of 99 5%. When considering the HRmax obtained on CPX as 100%, the HRmax Table 1
General characteristics of the study population.
Variable
N = 46
Age, years Weight, kg Height, cm Body mass index, kg m2 Physical activity index
323 913 1614 351 68
78 114 55 43 11
Values as mean SD.
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
€rgensen et al. 123 Shuttle walking test in obese women: test-retest, S. P. Ju
P
ISWT3
Variable
ISWT2
ISWTD, m ISWTD% predict, % Speed, km/h VO2, ml min1 VCO2, ml min1 VO2, ml kg1 min1 Ventilation, l min1 Respiratory rate, rpm Heart rate rest, bpm Heart rate peak, bpm Heart rate max, predict, % SBP rest, mmHg SBP peak, mmHg DBP rest, mmHg DBP peak, mmHg
463 823 60 1663 16046 183 52 347 874 150 842
92 161 06 351 3942 4 13 85 11 18 9
1146 161 78 794
9 19 9 12
467 829 61 1702 16757 188 55 340 870 148 835
99 176 06 361 4580 42 16 82 11 18 9
084 085 054 060 062 086 033 070 084 074 072
1146 159 766 792
10 18 8 11
096 054 045 093
HR peak – ISWT2 e ISWT3 (bpm)
ISWTD, incremental shuttle walking test distance; VO2, oxygen uptake; VCO2, carbon dioxide production; SBP, systolic blood pressure; DBP, diastolic blood pressure. Results expressed as mean SD.
25
95% confidence interval Variable
Intraclass correlation
Lower bound
Upper bound
ISWTD, m Speed, km h1 Ventilation, l/min VO2, ml min1 VO2, ml kg1 min1 VCO2, ml min1
0926 0836 0776 0890 0900 0865
0866 0703 0595 0801 0820 0756
0959 0909 0876 0939 0945 0925
ISWTD, incremental shuttle walking test distance; VO2, oxygen uptake; VCO2, carbon dioxide production.
Discussion The aim of this study was to test the reliability and validity of the ISWT in a cohort of obese women. We found that, after a familiarization test, key variables form the ISWT in this population were highly reproducible. Moreover, significant correlations between peak VO2 during CPX and ISWT variables were demonstrated. These findings indicate the ISWT may be a valuable clinical assessment technique in adult females with obesity. To minimize higher influences brought about by the process of ageing, our study restricted the sample to adult women of childbearing age. Although we included women from all three obesity grades, the sample had an average BMI equivalent to grade II1, considered important for its association with comorbidities and significant changes that affect physical performance (Zavorsky, 2009). Additionally, the
(a) +1.96 SD 18.4
20 15 10 5
Mean 2.0
0
–5 –10 –1.96 SD –14.4
–15
Figure 1 A Bland–Altman plot of the between-test differences. The 95% confidence intervals for the incremental shuttle walking test (ISWT) and cardiopulmonary exercise test. Mean bias SD for ISWT2 and ISWT3. (a) Heart rate peak between ISWT2 and ISWT3; (b) Respiratory rate ISWT2 and ISWT3; (c) VO2peak ISWT2 and ISWT3; (d) ISWTD ISWT2 and ISWT3. HR, heart rate; RR, respiratory rate; VO2, oxygen uptake; ISWT2, second incremental shuttle walk test; ISWT3, third incremental shuttle walk test.
VO2 peak – ISWT2 e ISWT3 (ml.kg–1.min–1)
–20 100
120 140 160 180 Average ISWT2 e ISWT3 (bpm)
(c)
4
200
+1.96 SD 3.5
3 2 1 0
Mean –0.5
–1 –2 –3 –4
–1.96 SD –4.5 10
15
20
25
Average ISWT2 e ISWT3 (ml.kg–1.min–1)
30
RR peak – ISWT2 e ISWT3 (br.min–1)
Table 2 Comparative evaluation of the second and third incremental shuttle walking test (ISWT2 and ISWT3) on physiologic and cardiovascular responses.
Table 3 Reliability between second and third incremental shuttle walking test (ISWT2 and ISWT3).
20
(b) +1.96 SD 14.3
15 10 5
Mean 0.7
0 –5 –10
+1.96 SD –12.8
–15 10
80 Distance – ISWT2 e ISWT3 (m)
during the ISWT was calculated. Using this calculation, the HRmax during the ISWT was 84% of the maximum obtained on CPX. Similarly, the percentage of VO2 for the ISWT was 854% of the peak value achieved during CPX. The main CPX variable selected to correlate with the responses obtained during the ISWT was VO2 in ml min1 and ml kg1 min1. Moderate correlations occurred between peak CPX with ISWTD and ISWT VO2 (Fig. 2).
40 50 20 30 Average ISWT2 e ISWT3(br.min–1)
(d)
60
+1.96 SD 70.2
60 40 20
Mean –5.9
0 –20 –40 –60
–1.96 SD –82.0
–80
–100 200
300 400 500 600 700 Average ISWT2 e ISWT3 (m)
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
800
€ rgensen et al. 124 Shuttle walking test in obese women: test-retest, S. P. Ju
800
(a)
700
ISWT (m)
600 500 400 300 200
r = 0,54; P < 0.0001 100 10
15
20
25
30
35
VO2 CPX on treadmill (ml.kg–1.min–1)
VO2 ISWT (ml.kg–1.min–1)
3000
(b)
2500
2000
1500
1000
500 10
r = 0,64; P < 0.0001 15
20
25
30
35
VO2 CPX on treadmill (ml.kg–1.min–1)
Figure 2 The linear relationship between (a) VO2peak arraigned at CPX and performance obtained at the ISWT (m), and (b) between relative VO2peak (in ml Kg1 min1) obtained CPX with the relative VO2 (in ml Kg1 min1) at ISWT. VO2, oxygen uptake; CPX, cardiopulmonary exercise test; ISWTD, distance walked on the incremental shuttle walk test; ISWT, incremental shuttle walk test.
majority of subjects had a low score on the Baecke questionnaire, indicating the group was primarily sedentary and thus of similar activity patterns. Singh et al. (Singh et al., 1992) developed the ISWT with the main objective to use this exercise assessment in the elderly population. For evaluation of young individuals, the most appropriate incremental test field is the shuttle run test (Leger & Gadoury, 1989). However, given the functional limitations precipitated by obesity, the ISWT may be appropriate in younger individuals with excess body mass. Given there are no previous studies assessing the applicability of the ISWT in the obese population, there is no consensus on the intensity of this test. Our results demonstrate the physiologic measures assessed during the ISWT approached maximal effort as compared to CPX, supporting the potential clinical utility of this assessment as a means to gauge functional capacity in obese patients; with mean percentage of HRmax ~84% and VO2 ~85% when compared to CPX, indicated the ISWT elicited a near-maximal effort. In relation to the learning effect, some studies (Dyer et al., 2002; Woolf-May & Ferrett, 2008) investigating other populations reported that employing two ISWTs can minimize
variability. Regarding the population of adult women with obesity, to our knowledge, there is no data assessing the ISWT learning effect. For this reason, we applied 2 tests (ISWT1 and ISWT2) on the same day, consistent with previous studies in other populations (Dyer et al., 2002; Woolf-May & Ferrett, 2008). To analyse reproducibility, the test (ISWT2) and retest (ISWT3) occurred on different days. We observed no significant differences for any variable studied, which supports reproducibility of this test for the cohort studied. In addition, we observed that the main variables were concordant, being considered reproducible. Therefore, there appears to be no reason to perform a refamiliarization procedure on the second day of testing, when the period between assessments is ≤7 days, which is consistent with other studies assessing different populations (Booth & Adams, 2001). In our study, the reproducibility was observed in the comparative analysis between the two ISWTs. van Bloemendaal et al. (2012) also showed good reproducibility for the ISWT in patients who suffered a stroke. In addition, to test the reliability of the application of ISWT, we selected the main variables obtained at the end of the exercise, which were analysed by the ICC. In the present study, we observed good ISWT reliability in obese women. Other studies have performed the ICC to assess reliability of the 6MWT (Booth & Adams, 2001; Beriault et al., 2009). Beriault et al., (Beriault et al., 2009) tested the reliability of 6MWT in obese adults, and the values demonstrated strong reliability. Recently, however, Dourado & Guerra (2013) observed high relative reliability and validity of heart rate variability threshold assessment during an ISWT in middle-aged and older adults. However, to our knowledge, the present study is the first to assess the reproducibility and validity of the ISWT in an obese population when compared with peak VO2 (a gold standard measurement). For this reason, we selected this protocol applied on a treadmill to compare metabolic and ventilatory measurements obtained during the ISWT, to validate this incremental walking testing. The data compared between the CPX and ISWT clearly demonstrated differences, with the former test appearing to illicit a maximal effort and the latter test being near-maximal. Even so, the efforts induced by the ISWT appeared to produce sufficient effort for a field test to provide a meaningful assessment of functional capacity and aerobic performance. In the present study, peak VO2 was selected as the main variable to compare agreement between tests, an approach which is consistent with other studies (Luxton et al., 2008; Struthers et al., 2008; Dourado & Guerra, 2013). The peak VO2 obtained during CPX is an important measurement in assessing patients with impaired cardiorespiratory fitness. However, the strongest correlations were obtained with peak VO2 in ml kg1 min1, which can be explained by excess body weight as a significant influencing factor with respect to cardiorespiratory fitness.
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
€rgensen et al. 125 Shuttle walking test in obese women: test-retest, S. P. Ju
In the present study, however, some limitations should be considered. Firstly, our study evaluated relatively young obese women. Thus, obese men and other age groups irrespective of gender should be investigated in future trials to confirm the findings reported here. Secondly, we compared metabolic and cardiovascular responses between maximal CPX using the Bruce protocol, which incorporated incremental adjustments of treadmill-controlled speed and inclination. On the other hand, the ISWT was performed on a level surface with incremental adjustments only in patient-controlled speed. However, protocols that include only an increase in speed could limit this population due to difficulty running, especially those with grade III obesity. The differences in protocols may have influenced the comparability of data and should be addressed by future investigations. We conclude that the ISWT may be an important tool for the cross-sectional evaluation of physical fitness in obese adult females, demonstrating acceptable reliability and validity. Furthermore, the ISWT may also have longitudinal utility in evaluating the efficacy of programmes for weight loss and other rehabilitative strategies.
Acknowledgments The authors thank all colleagues from the Cardiopulmonary Physiotherapy Laboratory of Physiotherapy Department, Federal University of Sao Carlos (UFSCar), Brazil) for their collaboration and the voluntaries for their effort and enthusiastic cooperation throughout the study.
Funding The study received financial support from the Fundac~ao de Amparo a Pesquisa do Estado de Sao Paulo, Sao Paulo, Brazil (FAPESP 2009/01842-0). Soraia Pilon J€ urgensen is a Master student of the same institution (FAPESP-2010/03030-0). AB-S is an Established Investigator (level II) of the Conselho Nacional de Desenvolvimento Cientıfico e Tecnol ogico (CNPq), Brazil.
Conflict of interest The authors declare no conflict of interest.
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doi: 10.1111/cpf.12135
Shuttle walking test in obese women: test-retest reliability and concurrent validity with peak oxygen uptake €rgensen1, Renata Trimer1, Victor Z. Dourado2, Luciana Di Thommazo-Luporini1, Soraia P. Ju audio R. Oliveira4, Ross Arena5, Renata G. Mendes1 and Audrey Borghi-Silva1 Jose C. Bonjorno-Junior3, Cl 1
Cardiopulmonary Physiotherapy Laboratory, Federal University of Sao Carlos, Sao Carlos, 2Department of Human Movement Sciences, Laboratory of Human Motricity, Federal University of S~ao Paulo, Santos, 3Department of Bioengineering, University of Sao Paulo, 4Department of Medicine, Federal University of Sao Carlos, Sao Carlos, Brazil and 5Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois Chicago, Chicago, IL, USA
Summary Correspondence Audrey Borghi-Silva, Federal University of Sao Carlos (UFSCar), Cardiopulmonary Physiotherapy Laboratory – Physical Therapy Department, Rodovia Washington Luis, Km 235-SP310, Sao Carlos, 13565-905, Sao Paulo, Brazil E-mail: [email protected]
Accepted for publication Received 23 October 2013; accepted 13 January 2014
Key words cardiopulmonary response; metabolic stress; obesity; oxygen uptake; physical capacity; submaximal exercise testing; women
Objective The aim of this study was to evaluate the test–retest reliability, concurrent validity and agreement with peak oxygen uptake (VO2) obtained during cardiopulmonary exercise testing (CPX) on a treadmill for the incremental shuttle walking test (ISWT) in obese women. Methods Prospective study with a convenient sample of 46 community-dwelling obese women (BMI > 30 kg m2). The main outcome measures were walking distance on the ISWT and peak VO2. Results Test–retest reliability was good to excellent for the exercise tests (ISWT distance ICC: 090; and CPX peak VO2 ICC: 090). Peak VO2 obtained during CPX correlated significantly with ISWT distance (r = 054, P08 good;
>09 excellent; Cronbach, 1951); (iv) Pearson’s or Spearman’s coefficient of correlation to study the correlation between variables [perfect correlation (r = 1), strong (r > 075), moderate (r > 05), weak (r < 05) and non-existent (r = 0)]. The level of statistical significance was set at P40 kg m2). Regarding self-reported physical activity, 83% of the participants evaluated in this study were considered sedentary and 17% reported a normal physical activity index. None of the subjects included in this analysis had a high level of physical activity (Pepera et al., 2013). Of hypertensive volunteers (n = 8), all were managed pharmacologically and showed no hypertensive crisis. As demonstrated in Table 2, there was no statistical difference for any variable analysed between ISWT2 and ISWT3. During ISWT2, the group walked an average of 82 16% of the predicted distance, and during ISWT3, this value was 83 17% (P = 084). Several key variables were selected to assess the reliability between ISWT2 and ISWT3: HR, respiratory rate (RR), VO2 and ISWTD. We observed that the mean difference between these variables approximated zero, suggesting good concordance between ISWT2 and ISWT3 (Fig. 1). The reliability of key variables is listed in Table 3; all demonstrated high reliability, in particular, ISWTD. As there was no significant difference between the values obtained for ISWT2 and ISWT3, the former was selected for a validation analysis in comparison with the data obtained from the CPX on a treadmill. It was noted that the ISWT represented near-maximum effort in this population with a mean HRmax value of 83 9%, while the CPX was consistent with maximal effort and had a HRmax average of 99 5%. When considering the HRmax obtained on CPX as 100%, the HRmax Table 1
General characteristics of the study population.
Variable
N = 46
Age, years Weight, kg Height, cm Body mass index, kg m2 Physical activity index
323 913 1614 351 68
78 114 55 43 11
Values as mean SD.
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
€rgensen et al. 123 Shuttle walking test in obese women: test-retest, S. P. Ju
P
ISWT3
Variable
ISWT2
ISWTD, m ISWTD% predict, % Speed, km/h VO2, ml min1 VCO2, ml min1 VO2, ml kg1 min1 Ventilation, l min1 Respiratory rate, rpm Heart rate rest, bpm Heart rate peak, bpm Heart rate max, predict, % SBP rest, mmHg SBP peak, mmHg DBP rest, mmHg DBP peak, mmHg
463 823 60 1663 16046 183 52 347 874 150 842
92 161 06 351 3942 4 13 85 11 18 9
1146 161 78 794
9 19 9 12
467 829 61 1702 16757 188 55 340 870 148 835
99 176 06 361 4580 42 16 82 11 18 9
084 085 054 060 062 086 033 070 084 074 072
1146 159 766 792
10 18 8 11
096 054 045 093
HR peak – ISWT2 e ISWT3 (bpm)
ISWTD, incremental shuttle walking test distance; VO2, oxygen uptake; VCO2, carbon dioxide production; SBP, systolic blood pressure; DBP, diastolic blood pressure. Results expressed as mean SD.
25
95% confidence interval Variable
Intraclass correlation
Lower bound
Upper bound
ISWTD, m Speed, km h1 Ventilation, l/min VO2, ml min1 VO2, ml kg1 min1 VCO2, ml min1
0926 0836 0776 0890 0900 0865
0866 0703 0595 0801 0820 0756
0959 0909 0876 0939 0945 0925
ISWTD, incremental shuttle walking test distance; VO2, oxygen uptake; VCO2, carbon dioxide production.
Discussion The aim of this study was to test the reliability and validity of the ISWT in a cohort of obese women. We found that, after a familiarization test, key variables form the ISWT in this population were highly reproducible. Moreover, significant correlations between peak VO2 during CPX and ISWT variables were demonstrated. These findings indicate the ISWT may be a valuable clinical assessment technique in adult females with obesity. To minimize higher influences brought about by the process of ageing, our study restricted the sample to adult women of childbearing age. Although we included women from all three obesity grades, the sample had an average BMI equivalent to grade II1, considered important for its association with comorbidities and significant changes that affect physical performance (Zavorsky, 2009). Additionally, the
(a) +1.96 SD 18.4
20 15 10 5
Mean 2.0
0
–5 –10 –1.96 SD –14.4
–15
Figure 1 A Bland–Altman plot of the between-test differences. The 95% confidence intervals for the incremental shuttle walking test (ISWT) and cardiopulmonary exercise test. Mean bias SD for ISWT2 and ISWT3. (a) Heart rate peak between ISWT2 and ISWT3; (b) Respiratory rate ISWT2 and ISWT3; (c) VO2peak ISWT2 and ISWT3; (d) ISWTD ISWT2 and ISWT3. HR, heart rate; RR, respiratory rate; VO2, oxygen uptake; ISWT2, second incremental shuttle walk test; ISWT3, third incremental shuttle walk test.
VO2 peak – ISWT2 e ISWT3 (ml.kg–1.min–1)
–20 100
120 140 160 180 Average ISWT2 e ISWT3 (bpm)
(c)
4
200
+1.96 SD 3.5
3 2 1 0
Mean –0.5
–1 –2 –3 –4
–1.96 SD –4.5 10
15
20
25
Average ISWT2 e ISWT3 (ml.kg–1.min–1)
30
RR peak – ISWT2 e ISWT3 (br.min–1)
Table 2 Comparative evaluation of the second and third incremental shuttle walking test (ISWT2 and ISWT3) on physiologic and cardiovascular responses.
Table 3 Reliability between second and third incremental shuttle walking test (ISWT2 and ISWT3).
20
(b) +1.96 SD 14.3
15 10 5
Mean 0.7
0 –5 –10
+1.96 SD –12.8
–15 10
80 Distance – ISWT2 e ISWT3 (m)
during the ISWT was calculated. Using this calculation, the HRmax during the ISWT was 84% of the maximum obtained on CPX. Similarly, the percentage of VO2 for the ISWT was 854% of the peak value achieved during CPX. The main CPX variable selected to correlate with the responses obtained during the ISWT was VO2 in ml min1 and ml kg1 min1. Moderate correlations occurred between peak CPX with ISWTD and ISWT VO2 (Fig. 2).
40 50 20 30 Average ISWT2 e ISWT3(br.min–1)
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Mean –5.9
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–1.96 SD –82.0
–80
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300 400 500 600 700 Average ISWT2 e ISWT3 (m)
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
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€ rgensen et al. 124 Shuttle walking test in obese women: test-retest, S. P. Ju
800
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r = 0,54; P < 0.0001 100 10
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r = 0,64; P < 0.0001 15
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VO2 CPX on treadmill (ml.kg–1.min–1)
Figure 2 The linear relationship between (a) VO2peak arraigned at CPX and performance obtained at the ISWT (m), and (b) between relative VO2peak (in ml Kg1 min1) obtained CPX with the relative VO2 (in ml Kg1 min1) at ISWT. VO2, oxygen uptake; CPX, cardiopulmonary exercise test; ISWTD, distance walked on the incremental shuttle walk test; ISWT, incremental shuttle walk test.
majority of subjects had a low score on the Baecke questionnaire, indicating the group was primarily sedentary and thus of similar activity patterns. Singh et al. (Singh et al., 1992) developed the ISWT with the main objective to use this exercise assessment in the elderly population. For evaluation of young individuals, the most appropriate incremental test field is the shuttle run test (Leger & Gadoury, 1989). However, given the functional limitations precipitated by obesity, the ISWT may be appropriate in younger individuals with excess body mass. Given there are no previous studies assessing the applicability of the ISWT in the obese population, there is no consensus on the intensity of this test. Our results demonstrate the physiologic measures assessed during the ISWT approached maximal effort as compared to CPX, supporting the potential clinical utility of this assessment as a means to gauge functional capacity in obese patients; with mean percentage of HRmax ~84% and VO2 ~85% when compared to CPX, indicated the ISWT elicited a near-maximal effort. In relation to the learning effect, some studies (Dyer et al., 2002; Woolf-May & Ferrett, 2008) investigating other populations reported that employing two ISWTs can minimize
variability. Regarding the population of adult women with obesity, to our knowledge, there is no data assessing the ISWT learning effect. For this reason, we applied 2 tests (ISWT1 and ISWT2) on the same day, consistent with previous studies in other populations (Dyer et al., 2002; Woolf-May & Ferrett, 2008). To analyse reproducibility, the test (ISWT2) and retest (ISWT3) occurred on different days. We observed no significant differences for any variable studied, which supports reproducibility of this test for the cohort studied. In addition, we observed that the main variables were concordant, being considered reproducible. Therefore, there appears to be no reason to perform a refamiliarization procedure on the second day of testing, when the period between assessments is ≤7 days, which is consistent with other studies assessing different populations (Booth & Adams, 2001). In our study, the reproducibility was observed in the comparative analysis between the two ISWTs. van Bloemendaal et al. (2012) also showed good reproducibility for the ISWT in patients who suffered a stroke. In addition, to test the reliability of the application of ISWT, we selected the main variables obtained at the end of the exercise, which were analysed by the ICC. In the present study, we observed good ISWT reliability in obese women. Other studies have performed the ICC to assess reliability of the 6MWT (Booth & Adams, 2001; Beriault et al., 2009). Beriault et al., (Beriault et al., 2009) tested the reliability of 6MWT in obese adults, and the values demonstrated strong reliability. Recently, however, Dourado & Guerra (2013) observed high relative reliability and validity of heart rate variability threshold assessment during an ISWT in middle-aged and older adults. However, to our knowledge, the present study is the first to assess the reproducibility and validity of the ISWT in an obese population when compared with peak VO2 (a gold standard measurement). For this reason, we selected this protocol applied on a treadmill to compare metabolic and ventilatory measurements obtained during the ISWT, to validate this incremental walking testing. The data compared between the CPX and ISWT clearly demonstrated differences, with the former test appearing to illicit a maximal effort and the latter test being near-maximal. Even so, the efforts induced by the ISWT appeared to produce sufficient effort for a field test to provide a meaningful assessment of functional capacity and aerobic performance. In the present study, peak VO2 was selected as the main variable to compare agreement between tests, an approach which is consistent with other studies (Luxton et al., 2008; Struthers et al., 2008; Dourado & Guerra, 2013). The peak VO2 obtained during CPX is an important measurement in assessing patients with impaired cardiorespiratory fitness. However, the strongest correlations were obtained with peak VO2 in ml kg1 min1, which can be explained by excess body weight as a significant influencing factor with respect to cardiorespiratory fitness.
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd 35, 2, 120–126
€rgensen et al. 125 Shuttle walking test in obese women: test-retest, S. P. Ju
In the present study, however, some limitations should be considered. Firstly, our study evaluated relatively young obese women. Thus, obese men and other age groups irrespective of gender should be investigated in future trials to confirm the findings reported here. Secondly, we compared metabolic and cardiovascular responses between maximal CPX using the Bruce protocol, which incorporated incremental adjustments of treadmill-controlled speed and inclination. On the other hand, the ISWT was performed on a level surface with incremental adjustments only in patient-controlled speed. However, protocols that include only an increase in speed could limit this population due to difficulty running, especially those with grade III obesity. The differences in protocols may have influenced the comparability of data and should be addressed by future investigations. We conclude that the ISWT may be an important tool for the cross-sectional evaluation of physical fitness in obese adult females, demonstrating acceptable reliability and validity. Furthermore, the ISWT may also have longitudinal utility in evaluating the efficacy of programmes for weight loss and other rehabilitative strategies.
Acknowledgments The authors thank all colleagues from the Cardiopulmonary Physiotherapy Laboratory of Physiotherapy Department, Federal University of Sao Carlos (UFSCar), Brazil) for their collaboration and the voluntaries for their effort and enthusiastic cooperation throughout the study.
Funding The study received financial support from the Fundac~ao de Amparo a Pesquisa do Estado de Sao Paulo, Sao Paulo, Brazil (FAPESP 2009/01842-0). Soraia Pilon J€ urgensen is a Master student of the same institution (FAPESP-2010/03030-0). AB-S is an Established Investigator (level II) of the Conselho Nacional de Desenvolvimento Cientıfico e Tecnol ogico (CNPq), Brazil.
Conflict of interest The authors declare no conflict of interest.
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